Tracing the source of mercury pollution

(21.12.2011)

Using the mercury isotopic pattern as a kind of fingerprint holds promise as a tool to assist in the identification of local Hg deposition related to anthropogenic emissions.

Background:Mercury ic called a global pollutant. Humans pump thousands of tons of vapor from the metallic element mercury into the atmosphere each year. According to EPA the largest manmade source of mercury emissions in the U.S. comes from coal-burning power plants. It is the chemical form of mercury released into the atmosphere that dictates whether it remains suspended for long periods and therefore can travel even across continents or gets removed from the atmosphere by precipitation. Therefore it is an ongoing discussion, about where that mercury goes when it’s released from a power plant smokestack.

The new study:Now a research group from the University of Michigan have started to crack the puzzle of how much is deposited nearby, close to the plant, and how much goes into what is called the global pool of mercury.

Joel Blum and his colleagues, using the isotopic pattern of mercury as a fingerprint were able to track mercury emissions from a power plant in Florida... and they found that a high proportion of the mercury ended up nearby.The team took the fingerprint of mercury isotope ratios in coal from the regions in Kentucky and West Virginia that supply the Florida power plant. They further measured rainfall at sites near the plant and sites far away from the plant for a month. By comparing the fingerprints of mercury from the coal and the rainfall it turned out that the mercury fingerprint in those rainfall samples near the plant was very different from the mercury coming from other sources from across the Gulf of Mexico. In essence, the results basically indicated that a large portion of the mercury is being deposited locally from a particular power plant which strengthens the argument that mercury emissions from power plants in the United States should be regulated in order to reduce mercury pollution across the US.

A lot of questions remain to be solved to make this new technique an informative tool. Does the mercury fingerprint from coal show up unaltered in the stack gases? Can the fingerprints from other power plants really be distinguished ? Can the amount of mercury coming from a particular source be quantitatively estimated ? More work seems to be necessary in order to develop this new method.